Method and system for high speed photolithography

ABSTRACT

A method and system for modification of a pattern on a semiconductor  subste, comprising the application of an electrical current through a liquid medium having a series of individual pixels controlled by a computer, thereby causing the clear liquid to change to opaque in selected areas.

The invention described herein may be manufactured, used, and licensedby or for the Government for Governmental purposes without the paymentto us of any royalties thereon.

BACKGROUND OF INVENTION

1. Field of Invention

This invention relates to a method and system for the patterning wafersat high speed without the generation of a photomask.

2. Brief description of the Prior Art

In the production of integrated circuits, computer designed patterns areused to delineate areas on the circuit. For each item produced, up totwenty or more different patterns are used, i.e., one for each level ofthe circuit. There are currently two methods for transferring patternsonto semiconductor substrates.

The first method uses a glass plate with chrome and photosensitive layeron it. After the pattern is designed on the computer, a special camerais used to expose the photosensitive layer. The photosensitive layer isthen developed and the chrome is etched away in the exposed area.

This mask is then used to pattern the intergrated circuit through theuse of another camera. The camera aligns the photomask with the waferand then floods the mask with light, allowing light only to pass througharea where the chrome is removed, thus exposing the wafer. In this waythe entire circuit is patterned all at one time. The advantage of thismethod is the speed in which the wafer can be exposed. In a productionfabrication facility over 40 wafer are treated each hour for each foreach patterning system.

A disadvantage of this system is that a new mask must be produced foreach level of the circuit. This adds up to thousands of masks for aproduction facility. An other disadvantage is that the a new mask mustbe produced for any change of mask set.

Another method for patterning an integrated circuit is through the useof a beam writing tool. This tool uses a focused scan of particles, suchas an electron beam, or an ion beam to expose the photosensitivematerial on the wafer. In this method, each circuit is exposed using abeam that is millions of times smaller than the area of the circuit. Thebeam then has to scan the entire surface area of the circuit. Theadvantage of this method is that the pattern being exposed on the wafercan be changed by varying the data fed into the beam writing tool. Theneed for creating a photomask first is eliminated. The disadvantage ofthe method is the speed at which the tool writes the patterns. Withthese systems, i.e., 6 wafers per hour can be run through the system.This is a problem in production where a level of 60 wafers per hourwould be desirable.

SUMMARY OF INVENTION

The present invention relates to a system and method for patterningwafer at high speed without the generation of a photomask. The methoduses a liquid crystal display (LCD) which is positioned between thelayers of a plastic material. A series of wires extend from the plasticmaterial into the LCD. A series of pixels are positioned at the bottomof the lower crystal materials. The pixels are controlled by a computer.The mask can either be contact printed directly on the circuit, or theimage can be optically controlled.

OBJECTS OF THE INVENTION

It is an object of the invention to provide and disclose a method forthe fabrication of semiconductor.

It is a further object of this invention to provide and disclose asystem for the fabrication of semiconductors obviating the need for adifferent pattern for each level of the circuit.

It is a further object of this invention to provide and disclose amethod for the fabrication of a semicoductor wherein the mask can becontact printed directly on the circuit.

It is a further object of the invention to provide and disclose a methodfor the fabrication of a semiconductor wherein the image can beoptically controlled.

Other objects and a fuller understanding of the invention may beascertained from the following drawings, description and claims.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is schematic view of the system utilized to carry out theinvention.

FIG. 2 is a plan view of the LCD component of FIG. 1.

FIG. 3 is a sectional view 3'--3' of FIG. 2.

FIG. 4 is a plan view of the bottom component 16 of the LCD.

DESCRIPTION OF PREFERRED EMBODIMENT

The present invention proposes the use of a modifiable mask for theproduction of intergrated circuits. This method uses a computer tochange the mask as required. The mask can be changed as often as needed.

Referring now to FIG. 2 of the drawings, the present invention comprisesLCD 10 which consists essentially of encased liquid 12 sandwichedbetween top section 14, and bottom section 16. A series of pixels 18 arepositioned on the interior bottom section of component 16. Each of thepixels are individually responsive to the signal from the computer. TheLCD IS commercially available from Sharp Electronics. The liquidemcompassed in the LCD is proprietary.

Clear wire 20 runs through the crystal. When a current is applied to thepixels the liquid becomes opaque along the wire. By connecting the wireto a computer or controller, specific areas of the LCD can be turned onor off. The computer controls which areas of the LCD are opaque, thuscreating a mask. If a change is to be made to the mask, the computerturns off certain areas of the LCD and/or turns on other areas. Thiswill allow rapid change in the design, while allowing the high speedpatterning available with the photomask method of patterning .

The alignments system comprises light source 26 positioned above LCDmeans 14. The light source may have shade means 28 to direct andrestrict the light to the LCD means. The LCD means are suitableconnected to power and computer means 30. The work piece 32 (wafer) ispositioned a suitable distance beneath the LCD means.

In operation, the mask design is entered into computer controller 30.Work piece 32 (substrate) is aligned into the system. The mask from thecomputer is fed into programmable mask 14. The programmable mask isaligned with the work piece using alignment marks programmed into thepattern data. The work piece is exposed through the programmable mask bymeans of lamp 26. The workpiece is removed, and the above steps arerepeated for each different mask required to complete the mask.

There are several advantages in the utilization of the presentinvention. It is possible to perform several different chip designdesigns on one mask, thereby eliminating the need to produce a mask forlayer of the circuit. Further, the mask can be printed directly on theindividually controlled circurity. Although we have described ourinvention with a certain degree of particularity, it is understood thatmodification may be made without departing from the spirit and scope ofthe present invention as herein claimed.

Having described our invention, we claim:
 1. A system for the productionof an intergrated circuit comprising:a computer, a programmable mask, acomputer controller designed to feed a mask design into the programmablemask, a work piece aligned with the programmable mask, and means forexposing the work piece through the programmable mask.
 2. A system inaccordance with claim 1, wherein the programmable mask comprisesa topand bottom component composed of a clear plastic, a clear liquidencompassed within the programmable mask at the midsection thereof, aseries of pixels positioned in the interior of the bottom component ofthe programmable mask so as to react with the liquid on command from thecomputer.
 3. A method for the production of intergrated circuits for theproduction of intergrated circuits comprising the steps of:entering amask design into a computer controller, feeding mask from the computercontroller into a programmable mask, aligning the programmable mask witha work piece, and exposing the work piece through the programmable mask.